1. Field of the Invention
The present invention relates to a chopper folding machine in a folding apparatus put in juxtaposition with a printing machine, and more particularly to a chopper folding machine which adjusts the timing of chopper folding effectively and is capable of detecting an inferior signature.
2. Description of the Related Art
In a conventional rotary press printing machine, a chopper blade and a conveyor belt of a chopper folding machine are driven synchronously using a driving system for the folding apparatus to cause conveyance of a signature, to be folded, by the conveyor belt and vertical movement of the chopper blade to be timed in order to perform chopper folding.
If the speed of the conveyor belt changes depending on a change in the printing speed, the timing of chopper folding of the signature may deviate from a reference one due to slippage of the signature on the belt, the inertia of the signature, etc. This may cause the signature to be broken or damaged to thereby provide a bad product. Thus, when the timing of the chopper folding deviates, it is necessary to time vertical movement of the chopper blade and conveyance of the signature.
Conventionally, the adjustment of such timing is performed by adjusting the meshing of bevel gears provided in the drive system for the chopper blade, namely, by moving one movable bevel gear relative to another fixed bevel gear to change the meshing and hence the phase angle of rotation of the chopper blade drive system to thereby adjust the vertical movement of the chopper blade.
However, the range of adjustment of the phase angles by changing the meshing of the bevel gears is proportional to their lead angles, whereas the range of movement of the movable bevel gear is limited to within the range of meshing of the fixed gear, so that if a deviation of the timing of chopper folding exceeds a limit, it is impossible to adjust the timing of chopper folding. Therefore, the machine must be stopped temporarily to adjust the timing, disadvantageously.
The adjustment of the timing of chopper folding is performed by the operator of the folder by visually observing the moment of chopper folding, namely, the timing at which the signature and the chopper blade contact and adjusting the meshing of the bevel gears if a deviation of the timing is found.
However, when the timing of chopper folding is observed visually, it cannot be found unless the deviation of the timing exceeds a certain value. Therefore, it takes significant time to find the deviation of the timing, so that the deviation becomes large and bad folding is likely to occur. Since it is difficult to automatically detect bad products such as broken or damaged ones, products will include both good and bad ones and, therefore, all the products must be inspected undesirably.
A personnel who supervises the timing of chopper folding, and hence the personnel expenditure, etc., are required. In addition, the personnel must supervise the chopper blade, etc., operating at considerably high speeds, which is a burden on him.
Furthermore, if the leading edge of the conveyed signature is tilted or not perpendicular to the conveyance direction, the chopper blade would fold the signature diagonally. In order to cope with this situation, a chopper stopper is provided above the conveyor belt to cause the signature to abut against the stopper to thereby correct the tilt of the sheet.
If the tilt of the signature is corrected by causing the sheet to abut against the stopper, it can be corrected so long as it is within a predetermined range. However, it cannot be corrected even if the sheet abuts against the chopper stopper if the tilt exceeds the predetermined range, and hence bad folding would occur undesirably. Therefore, the articles would include badly folded ones and hence all the articles must be inspected.
It is a first object of the present invention to provide a chopper folding machine which is capable of adjusting the timing of conveyance of the signature by the conveyor belt and of vertical movement of the chopper blade in a continuous stepless limitless manner and hence the timing of chopper folding without stopping the machine during the operation of the machine.
It is a second object of the present invention to provide a chopper folding machine which is capable of automatically adjusting the timing of chopper folding without relying on the operator.
It is a third object of the present invention to provide a chopper folding machine which is capable of automatically detecting a badly folded signature due to its tilt.